EDP Sciences
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Volume 371, Number 1, May III 2001
Page(s) 152 - 173
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20010309

A&A 371, 152-173 (2001)
DOI: 10.1051/0004-6361:20010309

Zero-metallicity stars

I. Evolution at constant mass
P. Marigo1, L. Girardi1, C. Chiosi1 and P. R. Wood2

1  Dipartimento di Astronomia, Università di Padova, Vicolo dell'Osservatorio 2, 35122 Padova, Italia
2  Mount Stromlo and Siding Spring Observatories, Australian National University, Private Bag, Weston Creek PO, ACT 2611, Australia

(Received 12 December 2000 / Accepted 28 February 2001)

We present extensive evolutionary models of stars with initial zero-metallicity, covering a large range of initial masses (i.e. $0.7 M_{\odot} \le M \le 100 M_{\odot}$). Calculations are carried out at constant mass, with updated input physics, and applying an overshooting scheme to convective boundaries. The nuclear network includes all the important reactions of the p-p chain, CNO-cycle and $\alpha$-captures, and is solved by means of a suitable semi-implicit method. The evolution is followed up to the thermally pulsing AGB in the case of low- and intermediate-mass stars, or to the onset of carbon burning in massive stars. The main evolutionary features of these models are discussed, also in comparison with models of non-zero metallicity. Among several interesting aspects, particular attention has been paid to describe: i) the first synthesis of 12C inside the stars, that may suddenly trigger the CNO-cycle causing particular evolutionary features; ii) the pollution of the stellar surface by the dredge-up events, that are effective only within particular mass ranges; iii) the mass limits which conventionally define the classes of low-, intermediate-, and high-mass stars on the basis of common evolutionary properties, including the upper mass limit for the achievement of super-Eddington luminosities before C-ignition in the high-mass regime; and iv) the expected pulsational properties of zero-metallicity stars. All relevant information referring to the evolutionary tracks and isochrones is made available in computer-readable format.

Key words: stars: evolution -- stars: interiors -- stars: Hertz sprung -- Russell (HR) diagram -- stars: low-mass

Offprint request: P. Marigo, marigo@pd.astro.it

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